Mayer started the two-year rotational training program to home-grow managers who would be “Googley.” The program has since become rather legendary, and former Google CEO Eric Schmidt told Steven Levy that he expects an APM alumni to run the company someday.

When you pick people who are leaders and show the sort of entrepreneurial zeal that makes them a great fit at Google, you also pick people who are confident enough to leave Google to build their own companies.

And a lot have.

“We get two to four good years, and if 20 percent stay with the company, that’s a good rate,” Mayer told Newsweek in 2007. “Even if they leave it’s still good for us. I’m sure that someone in this group is going to start a company that I will buy some day.”